All populations contain variation amongst individuals, and much of this variation has a genetic basis.
Genetic variation is present in humans, cats, peaches, Palmetto trees, mosquitos, bacteria... etc.
Understanding the processes and mechanisms resulting in genetic variation is important in health, agriculture, and ecology.

What We Do: In the Lawton-Rauh Laboratory, we test for mechanisms responsible for observed patterns of variation in plants. We study rice and amaranths as model systems for understanding population level processes that lead to adaptation, speciation and evolutionary relationships amongst groups, and long-term diversity in protein functions (molecular evolution). Many genetic phenomena can only be observed at the population level. Thus, it is important to look at entire populations – not just individuals – when studying genetics.

Why: Agroecosystems and crop species complexes are excellent, tractable systems for studying the genetic basis of adaptation and variation. With expanding genomic resources, we can use the power of comparing sequences amongst individuals and species to understand why some DNA sequences that code for proteins have different numbers of mutations than other sequences. Using population genetics platforms, we can determine if observed variation is due to different types of natural selection or neutral-equilibrium processes (like population size changes and founder effect) that shape variation across the entire genome. Because agriculture depends upon extensive knowledge of local and global environmental conditions over time, we can use recorded information about land use history to take into account specific factors that shape the environment, as well as stressors that may have been involved in observed variation. Within the last few decades, an explosion of resistance to herbicides plus documentations of gene flow between crop plants and wild relatives indicate that species can adapt very quickly to significant stressors. Because the most immediate stressors can be sequentially isolated, we have an amazing resource for studying how genome-level processes can lead to rapid adaptation at the population level. The most direct result is that we can translate fundamental evolutionary theories to tools to understand what the causes and consequences of agricultural history and practices in the field. It is our hope that our research will help others make informed decisions impacting food, fuel, and fiber cultivation.

Evolution in Action: Weeds in the Field

Crop Rice & Weedy Close RelativesWeedy red rice (Oryza sp.) is a conspecific weed of cultivated rice fields around the world. Red rice is classified as a noxious weed due to crop-like physiology, high fecundity and seed shattering, protracted emergence and seed dormancy. Red rice contamination in crops leads to large decreases in market value due to competition, lodging, and loss in value of harvested crop.

The Lawton-Rauh Lab is investigating :

Origins of California weedy rice and relationships among U.S. weedy rice populations

To understand the science behind variation, we look at different types of variation: genetic variation, trait (phenotype) variation, and environmental variation. We focus our experiments on the causes and consequences of genetic variation because it is the part of population variation that is passed down from one generation to the next generation, and subsequent generations.

Genetic variation comes from mutations in DNA sequences. DNA is molecule (deoxyribonucleic acid) that occurs as a sequence of nucleic acids (“A’s”, “T’s”, “C’s”, and “G’s”: adenine, thymine, cytosine, and guanine) and is inherited from parents to offspring.

Mutations in DNA lead to substitutions of one nucleic acid with another nucleic acid. An example is a replacement of “ATG” with “AGG” in a string of three nucleic acids. Strings of three nucleic acids code for a ‘codon’ that is translated into a specific amino acid. An example of a codon is “ATG” coding for the amino acid “methionine." Strings of amino acids make up proteins, and proteins are what orchestrate processes that make living things ‘alive!' Some nucleotide sequence replacements result in changes in amino acid sequences. These amino acid sequence changes sometimes change the protein structure enough that typical functioning of the protein and/or its pathway is disrupted or changed. In our lab, we study the population-level processes where mutations first occur in order to understand how such genetic variation leads to long term diversity of protein sequences and functions. Combining our work on genetic variation with trait variation and environmental variation helps us understand how all three types of variation (genetic, trait, and environment) result in adaptation and evolution over time. We focus primarily on population-level processes because adaptation and evolution are the result of changes in frequencies... and are not individual-level processes.